When control systems are installed in buildings, it is necessary to check--after having connected all installed cables, which connect a field unit, such as a temperature sensor or a motor actuator, to a switch cabinet--each individual one of these cables so as to find out whether the connection in question is correct. The course of action which has hitherto been taken for this purpose is that a first person stands near the switch cabinet and a second person near the respective field unit. The cable is tested by means of a so-called "continuity test". The two persons can communicate with the aid of a radio set so that it is also possible to carry out function tests of the field units. In principle, it can, however, only be checked whether or not the wiring was carried out correctly. If it is observed that a specific cable does not lead to the associated field unit, it is impossible to find out by means of the known method where the mistake has been made or rather where the cable actually leads to. In medium-sized building projects, between 3000 and 10,000 cables are tested in this way. In view of the fact that two persons are required for carrying out the test, it is easily imaginable that the testing of the wiring alone already entails considerable personnel expenditure. This expenditure is increased enormously if errors occur in the form of confusions. In view of the fact that the known method is not suitable for finding out where the cables which have been exchanged by mistake lead to, it will normally be necessary to install the whole wiring again. Since the construction is already in an advanced stage in this phase, costs will again be incurred, which are much higher than those entailed by the original wiring.
A method of the type mentioned at the beginning is known from AU-B-0551 and also from the reference document U.S. Pat. No. 3,891,811. An automatic conductor pair identifier utilizes a field unit under the control of an operator and an office control unit coupled to a multiwire cable of wire pairs to be identified. Upon actuation of the field unit by an operator, a frequency tone signal is transmitted over a randomly selected wire pair to the office control unit that responds thereto to transmit a pulse code representing a number identifying the wire pair over the same wire pair. This pulse code is received by the field unit and converted into a digital display for operator evaluation. Basically, the field unit comprises an oscillator coupled to a transmitter for generating the inquiring frequency signal. A pulse code is received in the field unit by a level detector/receiver coupled to logic circuitry for decoding the pulse code to drive a units display and a tens display as part of a digital readout. In the office unit, there is also a receiver and level detector coupled to logic circuitry for responding to an inquiring frequency signal to set up a counting sequence. Upon positively identifying an inquiring frequency signal, the logic circuitry actuates a transmitter coupled to an oscillator for transmitting the pulse coded to the field unit over the same wire pair used by the field unit.
Another method is known from periodical Elektor Electronics, vol. 16 (1990), April, No. 177, GB-London, article "Wiring Allocation Tester". Both methods include the steps of applying digital signals to one end of the cable cores with the aid of a multiplexer, said digital signals being adapted to be read at the other end of the cable by means of an associated receiver. Due to the multiplex operation used, the number of cable cores to be tested is limited.
Hence, it is the object of the present invention to improve a method according to the generic clause and an associated apparatus in such a way that an arbitrary number of cables can be tested.
The present invention is directed to a method of testing the wiring between a switch cabinet and field units which are connected to the switch cabinet and which are installed at a large distance therefrom. The method includes applying to all inputs or outputs of the switch cabinet which are provided with a cable core to be tested a digital address which is associated with the respective input or output and associating the addresses with the respective field units in a reference list. The address of the inputs or outputs of the switch cabinet are then interrogated via the cable cores connected thereto and compared with the reference list. A ground current is initiated by a manual testing unit at the end of the cable core to be tested which is located on the side of the field unit. The ground current causes the digital address of the input or output associated with the cable to be tested to be applied at least to the cable core to be tested.
In accordance with the present invention, this object is achieved by the end of the cable core which is located on the side of the field unit having applied thereto an identifying signal associated with the respective manual testing unit, the initiated ground current causing the cores of all cables to have applied thereto a combination of the identifying signal and of the address of the switch cabinet input or output associated with the cable core to be tested.
The advantage of the method according to the present invention is that an arbitrary number of addresses can be generated by the testing computer. The addresses are not continuously applied to the cable cores to be tested, but they are only called up when the cable core to be tested is connected to earth at the cable core end located on the side of the field unit. In other words, the cable to be tested is used as a communication cable by sending first an initiating signal from the manual testing unit to the testing computer, whereupon the address of the associated input or output of the switch cabinet is applied at least to the cable to be tested. To make things easier, this address is applied to all cables, since the other cables are at this time not connected to the manual testing unit so that reading of the addresses will not be carried out there. Since signals need not be compared in the manual testing unit, but only one single signal is read, transmission errors of the type occurring in connection with multiplex systems cannot be caused.
On the basis of this mode of operation, it is possible to test the wiring to be checked by a plurality of manual testing units at the same time. Each manual testing unit transmits an identifying signal of its own, which differs from the other identifying signals. When a ground current has been initiated on the cable core to be tested, the testing computer will apply to all cable cores the address of the associated input or output of the switch cabinet supplemented by the identifying signal of the manual testing unit. The address reader of the manual testing unit can only read addresses which have been supplemented by the identifying signal of its own manual testing unit. If a plurality of manual testing units is used, the same cable cores may thus have applied thereto different addresses at the same time; these addresses can, however, only be read by the respective associated manual testing unit. This method is particularly advantageous if extensive wirings of buildings are to be tested, since it will then be possible that several persons simultaneously test the wiring with different manual testing units, and it need not even be determined in advance which cable core will be checked by which person.
The measure of using the cable to be tested as a communication cable also permits a control signal to be transmitted from the manual testing unit to the testing computer, which will apply an operating voltage to the associated output of the switch cabinet. With the aid of this operating voltage, a function test of motor actuators or relays can then be carried out in addition to the testing of the wiring. In view of the fact that the control signal can be transmitted from the manual testing unit, the person performing the test can also carry out a visual inspection of the motor actuators or relays.
In order to supplement the above, it should additionally be stated that the initial transmission of the identifying signal to the testing computer permits the addresses to be stored together with the associated identifying signals so that, afterwards, it can be checked which cable or which output was tested by which manual testing unit, or rather whether an output was tested at all. On the basis of a list which is to be compiled making use of the data stored, it will then also be possible to check which cable has to be reconnected to which output or input of the switch cabinet.
In accordance with a further development, it will also be advantageous when the switch cabinet control means (DDC, SPS, etc.) is provided with a communication terminal which is adapted to have connected thereto the testing computer, and when the testing computer is constructed such that the signal "tested", which is transmitted by the manual testing unit, will start, upon being received by said testing computer, the reading and storing of a measurements record of the switch cabinet control means. It is thus possible to prepare records of the data measured at the switch cabinet control means during the function test of measuring field units, said data being then compared with values measured at the location of the measuring field unit. In view of the fact that this record is prepared simultaneously with the testing of the cables, the adjustment of the measuring field units can be carried out later on after the end of the whole cable testing at the switch cabinet control means (DDC, SPS, etc.).